AFAIR the notion of numeric synonyms was suggested to Diigo, but not adopted.
(Side note: in Diigo there does exist just a little synonymity, enough for tags to be case-insensitive in some but not all situations. I can't recall the exact detail, but there was careful thought to this.)
started by Chris 089 on 12 Mar 10
http://groups.diigo.com/group/Diigo_HQ/content/546457 (2007),
http://groups.diigo.com/group/Diigo_HQ/content/546475 (2007),
http://groups.diigo.com/group/Diigo_HQ/content/553997 (2008) and others may be of interest.
Synonymity of tags
> "süddeutsche" or "sueddeutsche" (US keyboard
> without the German umlauts available) or "sz", I always mean the same
> search for "sz" I will also find the other tags
The site that springs to mind is freshmeat.net, where it seems that each tag has a numeric synonym. Example:
http://handhelds.freshmeat.net/tags/iphone?with=2751&without=4759
AFAIR the notion of numeric synonyms was suggested to Diigo, but not adopted.
(Side note: in Diigo there does exist just a little synonymity, enough for tags to be case-insensitive in some but not all situations. I can't recall the exact detail, but there was careful thought to this.)
FWIW I use Common Tag format, with Faviki to help me http://groups.diigo.com/group/Diigo_HQ/content/592370